2. Summary of future projections

Projected changes over Japan for the end of the 21st century (future climate: 2076-2095 average) relative to the 20th century (present climate: 1980-1999 average) are summarized below.

Projected changes in temperature

The annual mean temperature is projected to increase by about 3°C in all regions. In particular, the northern part of Japan is expected to see the most significant rise (more than 3°C). For all regions, the increase in temperature is projected to be the largest in winter and the smallest in summer. In winter, the rise is expected to exceed 3°C in most regions except Okinawa/Amami. In particular, an increase of more than 3.5°C is expected in northern and eastern parts of Japan.

In the panel on the left, the red bars indicate future changes and the thin black lines show the standard deviation of interannual variability (left: present; right: future). In the panel on the right, red indicates increase and blue indicates decrease.

The 20-year return value (see Table 1.2-1) of annual maximum temperature is projected to increase within the range of 2-3°C, with the largest rise on the Pacific side of northern Japan. The 20-year return value of annual minimum temperature is projected to increase in the range of 2.5-4°C, with the largest rise also on the Pacific side of northern Japan.

The annual number of days with daily minimum temperatures below 0°C is projected to decrease in all regions, especially in the northern part of Japan. The annual number of days with daily maximum temperatures above 35°C is projected to increase from the eastern part of Japan to Okinawa/Amami, while the increase is expected to be relatively small in the northern part of Japan.

Fig. 2.1-4 Regionally averaged changes in the annual number of days with daily minimum temperatures below 0°C (left) and with daily maximum temperatures above 35°C (right)

In the panel on the left, the red bars indicate future changes and the thin black lines show the standard deviation of interannual variability (left: present; right: future). In the panel on the right, red (blue) indicates decrease (increase).

The pentad maximum snow depth is projected to decrease not only in peak months but also in autumn and spring, indicating that the snowy season will become shorter in the future. Meanwhile, snowfall change around the peak of winter is not expected to be as clear as in early or late winter. The seasonal peak of maximum snow depth is projected to come earlier in winter in the future climate than in the present climate.

2.4 Projected changes in other variables

Summer mean relative humidity is projected to decrease in most regions. Meanwhile, winter mean relative humidity is projected to increase in northern, eastern and western Japan except on the Sea of Japan side of eastern Japan.

Light blue and orange indicate that the absolute value of change is larger than interannual variability in the present climate period. Grey indicates that the change is not significant at a 90% confidence level.

The potential for the occurrence of severe weather events such as gusting winds and thunderstorms (evaluated in terms of the Energy Helicity Index) is projected to increase in all regions.